The goal of this project is to determine whether recombinant adeno-associated virus (rAAV)-mediated hepatic gene transfer will demonstrate preclinical feasibility and safety in the presence of underlying liver disease. This will be done in the context of developing vectors to treat alpha-1 antitrypsin deficiency (AATD)-related liver disease. AATD is relatively common single gene disease (carrier frequency of 4% in North Americans) characterized by both lung disease, which is thought to be due to a lack of function of AAT as a serum antiprotease, and liver disease, which is thought to be due to a toxic gain of function of mutant AAT within hepatocytes. The hepatocellular defect in AAT may relate to conformational properties of the common mutant forms of AAT, such as the PI*Z mutant (Glu342Lys) which impairs proper folding and can form stable polymers. AATD lung disease is currently being approached with intramuscular rAAV-mediated gene therapy by our group in clinical studies funded by NHLBI. However, since the liver disease is triggered by molecular events within individual hepatocytes, any gene therapy for AATD liver disease must entail genetic manipulation of the liver itself. Important work by several laboratories, including those of Drs. High, Kay, Wilson, and several others including our own, have demonstrated the feasibility of rAAV-mediated gene transfer to the liver with rAAV2 or with pseudotyped vectors utilizing alternative capsids, such as that of AAV serotype 8. We will investigate whether this apparent capability for safe and effective hepatocyte gene transfer will be affected by liver pathology (1) in a chimpanzee model of hepatitis C virus (HCV), an infection which is often encountered in patients who receive blood-product-derived IV protein replacements and (2) in mouse models of AATD. The goals of this project will be accomplished in 3 specific aims: (Aim 1) To determine if the safety, immunogenicity, or persistence of rAAV2-hAAT or rAAVS (pseudotype)-hAAT vectors are altered in the presence of chronic liver disease in primates;(Aim 2) To compare the relative efficacy in vivo of a number of molecular strategies for down-regulation of mutant AAT expression as a means to address AATD liver disease;and (Aim 3) To complete preclinical evaluation of the most promising gene therapy construct(s) derived from aim 2. The ultimate goal is to determine whether or not it is advisable to move forward with phase I clinical trials of rAAV vectors in the liver of AATD patients or other patients with underlying liver disease.